Field
This invention relates to thermosetting resin compositions useful for fluxing underfill applications, particularly in the form of a preapplied film.
Brief Description of Related Technology
Through silicon via (“TSV”) interconnection technology is gaining popularity due to its ability to increase computing capacity with lower power consumption using about the same real estate on a circuit board as traditional semiconductor packages. With TSV, interconnection is made between layered semiconductor die through the die itself rather than by a wire bonding technique around the periphery of the die as seen in die attach applications or through solder interconnection as is seen with capillary flow underfill applications.
In stacked die applications, the gap between die is quite narrow rendering application of capillary flow underfill difficult. While noflow underfill compositions are an option for flip chip assembly, there are recognized technical issues with this approach that has hindered its adoption commercially. See H. Lu et al. “No-flow Underfill Flip Chip Assembly—An Experimental And Modeling Analysis”, Microelec. Reliab., 42, 1205-12 (2001).
U.S. Pat. No. 7,213,739 (Wilson) describes and claims a fluxing curative for curing an underfill that comprises an epoxy resin and for fluxing a solder during a solder assembly of an electronic component to an electronic device substrate, the fluxing curative comprising a salt that is a reaction product of an imidazole component and a carboxylic acid component having at least 10 carbon atoms per molecule, where the carboxylic acid component is isostearic acid, 5-n-hexyl-2-(carboxyl-n-heptyl) cyclohex-3-ene carboxylic acid, or a combination thereof. The underfill is reported in the '739 patent to be a solution for application between an electronic component and an electronic device substrate to assist in solder assembly of the electronic component to the electronic device substrate and to provide mechanical shock resistance and thermal cycling resistance.
While the '739 patent describes an underfill based on a fluxing curative comprised of a salt that is a reaction product of an imidazole component and a carboxylic acid component having at least 10 carbon atoms per molecule, that approach has not been found to satisfy the demands of current commercial semiconductor packaging operations.
It would be desirable therefore to provide electronic packaging materials suitable for advanced applications, such as thermosetting resin compositions useful in stacked die applications, particularly those that use TSV interconnection technology.